A fluorescent lamp unit which can be used in place of an incandescent lamp has become popular these days. The fluorescent lamp unit of this type has a screw base which can be fitted into the incandescent lamp socket, and when the screw base is connected to the socket, the fluorescent lamp unit can be used in the same manner as the incandescent lamp.
Magnetic fields have been used in the past with both compact fluorescent lamps for use with incandescent fixtures as well as conventional and non-conventional fluorescent lamps. For example, U.S. Pat. No. 4,187,446, which issued to Gross et al on Feb. 5, 1980 and U.S. Pat. No. 4,311,942, which issued to Skeist et al on Jan. 19, 1982 disclose the use of an electromagnetic field generated by a specially designed ballast to spread the arc periodically throughout the volume of a compact fluorescent lamp.
U.S. Pat. No. 4,311,943, which issued to Gross et al on Jan. 19, 1982, combines the use of a recombination structure of fine fibers interposed in the arc path with an arc spreading coil which serves as all or part of the ballast of the fluorescent lamp.
U.S. Pat. No. 4,417,172, which issued to Touhou et al on Nov. 22, 1983, relates to suppressing low temperature flickering phenomena caused by moving striation in conventional fluorescent lamps by means of electromagnets or permanent magnets.
U.S. Pat. No. 4,434,385, which issued to Touhou et al on Feb. 28, 1984, suggests the use of a magnetic field locally disposed around a non-conventional lamp for varying the light distributing direction and/or color of the lamp.
The use of permanent magnets in compact fluorescent lamp unit designs of the present invention can make effective use of the available magnetic flux without requiring substantial changes in ballast design. The permanent magnetic flux available is constant during the entire lamp operating cycle thus providing a magnetic field even when the lamp current passes through zero. The ballast field is approximately 90 degrees out of phase with the current and light output, B is proportional to di/dt, thus the maximum ballast magnetic field occurs near zero light output which may not be optimum. Furthermore, practical ballast fields are of the order of 20 to 40 gauss whereas permanent magnets of several hundred gauss are easily obtainable. Additionally, generation of many ballast fields via coil windings may not be compatible with certain advanced ballast designs.